April 26, 2010

Deep Ocean Current Found Near Antarctica

A deep-ocean current has been discovered near Antarctica by scientists, saying that it has the volume of 40 Amazon Rivers and will help researchers study the impacts of climate change on the world's oceans.

The planet's climate relies heavily on the global ocean circulation pattern and the current discovered is a key part of that system. Evidence that the current exists had been detected previously by scientists, but there was no data on it.

"We didn't know if it was a significant part of the circulation or not and this shows clearly that it is," one of the authors, Steve Rintoul, told Reuters.

This is the fastest deep ocean current found to date, said Rintoul, of the Antarctic Climate and Ecosystems Cooperative Research Center in Hobart. The current has an average speed of nearly 8 inches per second and carries more than 39 million cubic feet per second of very cold water from Antarctica.

"At these depths, below two miles from the surface, these are the strongest recorded speeds we've seen so far, which was really a surprise to us," said Rintoul. The current carries dense, oxygen-rich water that sinks near Antarctica to the deep ocean basins further north around the Kerguelen Plateau in the southern Indian Ocean and then branches out, he added.

The current works together with a larger network of currents that span the oceans and work together as a giant conveyor belt carrying heat around the world.

The Gulf Stream brings warm water to the North Atlantic, giving northern Europe a relatively mild climate. If the current fails, as it has in the past, parts of Europe would be plunged into a deep freeze, according to scientists.

"The deep current along the Kerguelen Plateau is part of a global system of ocean currents called the overturning circulation, which determines how much heat and carbon the ocean can soak up," Rintoul said.

The circulation requires the creation of large volumes of very cold, salty water in several areas along coastal Antarctica that sinks to the bottom and flows to other ocean basins.

Scientists studied the sea floor at depths of about 3 miles for a two-year period, measuring current speeds, temperatures and salinity. "The continuous measurements provided by the moorings allow us, for the first time, to determine how much water the deep current carries to the north," said Rintoul.

He said a key issue for predicting climate was whether the overturning circulation was going to stay at its present strength or whether it was sensitive to changes as climate changes. More improvements to measuring the speed and volume of the water are needed to make more accurate predictions.

Australian and Japanese scientists published the study in Sunday's issue of the journal Nature Geoscience.


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